In solar generators a mode of operation has established itself in which the tracking operation is carried out step by step, e.g., in that a control seat valve is controlled to open and close again after about 15 seconds for a few seconds or fractions of a second with a lifting movement of a valve component. The reason is that a sensitive continuous regulation of a very small volume flow, as would be required for continuous tracking, has so far not been possible at reasonable costs and over a long service life. In the case of a solar trough, which may definitely have a length of e.g., 200 m, as the reflector of the solar generator with an absorber pipe in the focal point area, the absorber pipe is manufactured with such a great diameter (and because of the high internal pressure with a great wall thickness) that despite the continuous movement of the sun during standstill of the reflector between two tracking steps it always remains within the focal point area and shows optimum performance. In a tracking step the absorber pipe is so to speak slightly advanced relative to the sun, and the sun travels during standstill of the absorber pipe just up to the end of the focal point area before a new tracking step is carried out. In comparison with the mechanical and hydraulic components of the solar generator the costs of the absorber pipe are a very dominating factor. Likewise in the case of stepwise tracking the hydraulic cylinders must be configured to be big and strong so as to be able to perform at least every tracking step precisely and fast enough, and they are therefore also relatively expensive.
Prior art: EP 2 455 685 A, EP 2 226 592 A, U.S. Pat. No. 4,178,913 A, WO 2009/087257 A, DE 10 2008 050 250 A, DE 10 2006 040 962 A.